Nov 14, 2012 – NMR Topical Group Meeting

The North Jersey ACS NMR Topical Group proudly presented its November meeting at the Fuji Japanese Sushi & Seafood on Wednesday, November 14, 2012.

Abstract

The 2D structure of most small molecules can be in principle straightforwardly determined by manual or automatic analysis of a set of experimental data that includes the molecular formula, a series of 1D and 2D NMR experiments providing through-bond connectivity (COSY, TOCSY, HSQC, HMBC and ADEQUATE/INADEQUATE based experiments), and chemical shift predictions.

This is the main concept embedded in automatic structure elucidation programs. Once the 2D structure is available, the determination of the relative spatial arrangement (configuration and preferred conformation) of all atoms in the molecule is a more challenging task that it is commonly addressed in NMR by using NOE and 3J coupling constants analysis, as well as recent developments on the application of DFT calculation of 13C chemical shifts.

However, it is difficult to assess how many samples are sitting on the laboratory’s refrigerators waiting for an independent methodology that could lift some of the ambiguities generated by the use of conventional NMR methods. The development of the application of Residual Dipolar Couplings (RDCs) to the configurational and conformational analysis of small molecules has matured enough in the recent years to perform this task in an almost straightforward way, without even the need of using NOE and 3J coupling analysis, as it will be presented here for the analysis of rigid and semi-rigid small molecules.

The application of RDCs to the analysis of flexible molecules is still a field of research with plenty of room for development and a generally accepted approach is not available yet.